In the broadest sense, Magick is any act designed to cause intentional change. This term is often spelled with a terminal "k" to differentiate it from other practices, such as "stage magic". Magick is not capable of producing "miracles" or violating the physical laws of the universe (i.e. it cannot cause a solar eclipse), although "it is theoretically possible to cause in any object any change of which that object is capable by nature" (Book 4). Aleister Crowley saw magick as the essential method for a person to reach true understanding of the self and to act according to one's True Will. Crowley describes this process:

One must find out for oneself, and make sure beyond doubt, "who" one is, "what" one is, "why" one is...Being thus conscious of the proper course to pursue, the next thing is to understand the conditions necessary to following it out. After that, one must eliminate from oneself every element alien or hostile to success, and develop those parts of oneself which are specially needed to control the aforesaid conditions. (Book 4)

Crowley also provides us with some fundamental statements about the nature of magick (also from Book 4):

"MAGICK is the Science and Art of causing Change to occur in conformity with Will."

"Every intentional (willed) act is a Magical Act."

"Magick is the Science of understanding oneself and one's conditions. It is the Art of applying that understanding in action."

For Crowley, the practice of magick—although it equally applies to mundane things, like balancing the checkbook—is essentially to be used for attaining the Knowledge and Conversation of one's Holy Guardian Angel. Since achieving this state with one's 'Silent Self' can be extremely arduous, magick can be used not only to reach that particular goal, but to clear the way for it as well. For example, if one needed a particular dwelling to perform the operation, one could use magick to obtain a suitable home. Crowley stated that magick that did not have one of these goals as its aim was 'Black Magick' and should be avoided.

Traditional definitions

King Solomon, in his Lesser Key of the Goetia, says:

"Magic is the Highest, most Absolute, and most Divine Knowledge of Natural Philosophy, advanced in its works and wonderful operations by a right understanding of the inward and occult virtue of things; so that true Agents being applied to proper Patients, strange and admirable effects will thereby be produced. Whence magicians are profound and diligent searchers into Nature; they, because of their skill, know how to anticipate an effect, the which to the vulgar shall seem to be a miracle."

Modern definitions

In The Magick of Thelema, Lon Milo DuQuette expands on Crowley's definition of magick by saying that "conversely, any unwilled action is an unmagical act: reaching for a cigarette; ordering that fourth Martini; or any habitual or reactive behavior that overrides the momentum of one's life focus." He goes on to say that "magick also postulates a universal order—call it God, Nature, the Supreme Being, the Grand Architect of the Universe, the Tao, or just the-way-things-are. But the Magician knows that the pure Will of every man and every woman is already in perfect harmony with the divine Will; in fact they are one and the same. It is the Magician's Great Work to endeavor to remove the obstacles that hinder his or her perfect realization of that Will and then proceed to execute it."

Magick as ritual

Besides those willed acts that are of a mundane kind, such as balancing checkbooks, many instances of applied magick involve the use of rituals. Most magical rituals involve work with non-human beings (generally gods, but also demons, spirits, saints, Loa, etc.) and/or achieving non-normal psychological states (such as trance). There are many different purposes for conducting a magical ritual, including:

Systems of magick

Almost all cultures have developed some form of magic, although definitions and purposes have been highly variable. There is evidence of sophisticated systems of magic in many ancient civilizations, including the Greeks, Chinese, Egyptians, Jews, and even Christians. The following list includes systems of magick that are relatively modern, even if they have their roots in ancient systems.

History of Western European magic

Magical beliefs in Western Europe

Belief in various magical practices has waxed and waned in European and Western history, under pressure from either organized monotheistic religions or from skepticism about the reality of magic, and the ascendancy of scientism. The time of the Emperor Julian of Rome, marked by a reaction against the influence of Christianity, saw a revival of magical practices associated with neo-Platonism under the guise of theurgy.

In the Middle Ages

Mediæval authors, under the control of the Church, confined their magic to compilations of wonderlore and collections of spells. Albertus Magnus was credited, rightly or wrongly, with a number of such compilations. Specifically Christianized varieties of magic were devised at this period. During the early Middle Ages, the cult of relics as objects not only of veneration but also of supernatural power arose. Miraculous tales were told of the power of relics of the saints to work miracles, not only to heal the sick, but for purposes like swaying the outcome of a battle. The relics had become amulets, and various churches strove to purchase scarce or valuable examples, hoping to become places of pilgrimage. As in any other economic endeavor, demand gave rise to supply. Tales of the miracle-working relics of the saints were compiled later into quite popular collections like the Golden Legend of Jacobus de Voragine or the Dialogus miraculorum of Caesar of Heisterbach.

There were other, officially proscribed varieties of Christianized magic. The demonology and angelology contained in the earliest grimoires assume a life surrounded by Christian implements and sacred rituals. The underlying theology in these works of Christian demonology encourages the magician to fortify himself with fasting, prayers, and sacraments, so that by using the holy names of God, he can use divine power to coerce demons into appearing and serving his usually lustful or avaricious magical goals. Not surprisingly, the church disapproved of these rites; they are nonetheless Christianized for all that, and assume a theology of mechanical sacramentalism.

Magic in the Renaissance

Renaissance humanism saw a resurgence in hermeticism and other Neo-Platonic varieties of ceremonial magic. The Renaissance and the Industrial Revolution, on the other hand, saw the rise of scientism, in such forms as the substitution of chemistry for alchemy, the dethronement of the Ptolemaic theory of the universe assumed by astrology, the development of the germ theory of disease, that restricted the scope of applied magic and threatened the belief systems it relied on. Tensions roused by the Protestant Reformation led to an upswing in witch-hunting, especially in Germany, England, and Scotland; but ultimately, the new theology of Protestantism proved a worse foe to magic by undermining belief in the sort of ritualism that allowed religious rites to be re-purposed towards earthly, magical ends. Scientism, more than religion, proved to be magic's deadliest foe.

Alongside the ceremonial magic followed by the better educated was the everyday activities of folk practitioners of magic across Europe, typified by the cunning folk found in Great Britain. In their magical practices astrology, folklore, and distorted versions of Christian ritual magic worked alongside each other to answer customer demand.

Magic in the twentieth century

A further revival of interest in magic was heralded by the repeal, in England, of the last Witchcraft Act in 1951 EV. This was the cue for Gerald Gardner, now recognized as the founder of Wicca, to publish his first non-fiction book Witchcraft Today, in which he claimed to reveal the existence of a witch-cult that dated back to pre-Christian Europe. Gardner's new religion combined magic and religion in a way that was later to cause people to question the Enlightenment's boundaries between the two subjects.

Gardner's new religion, and many imitators, took off in the atmosphere of the 1960s and 1970s, when the counterculture of the hippies also spawned another period of renewed interest in magic, divination, and other occult practices. The various branches of neo-paganism and other new earth religions that have sprung up in Gardner's wake tend to follow his lead in combining the practice of magic and religion. The trend was continued by some heirs to the counterculture; feminists led the way when some launched an independent revival of goddess worship. This brought them into contact with the Gardnerian tradition of magical religion, and deeply influenced that tradition in return.